aardwrk make your own bulb with a red led just break the glass in the bulb and
heat up the solder in the center of the base and suction it out then removes all
the other crap in the base, If you have a 2 cell light then no resistor is needed
and you can wire the red led straight in. Go to that link and get the led with the
most mcd ones in the color you want and you can probably fit four leds in a 2
d maglight light base maybe more if you vary the height of the leads instead of
putting them side by side. You can carry a standard white led bulb in the base
and use the red then swap out if you need to.
I have a led light I got for christmas and it takes 3 aaa batts and has one of the
luxeon bulbs and it is bright as heck and the battery lasts close to a year using it
everyday to check my oil and do my pre trip inspection, It also has a blue lens
cover and a red one, the blue one doesn't hurt your night vision too bad and is way
brighter then the red one if you need more light. I think bass pro shops has a led
based light that has a red, blue, green and white led that is used for tracking wounded
animals since it makes the blood show up good.

 

This isn't really what you asked, but it might apply. I lost my 2AA cell Mag-Lite so replaced it with a 2AA cell LED Mag-Lite. The light is many times brighter, but for me, the batteries do not last as long. Bear in mind I would use the old style light's batteries until they were down to 1.25v each.

Now, this new light cuts off when the voltage approaches something like 1.3 or 1.4. I still use them in a portable radio that will use them down to 0.9v, so I don't mind the more frequent battery change. But be aware, there is no warning like in the old style with the light beam getting weaker. When these are ready to quit, they quit. You might get a couple of short bursts of light afterward, but pretty much that's it.

My 2 cents.